1. Field of Invention
This invention relates to the field of automotive restraints. More particularly, it relates to a self-inflating restraint for protecting occupants of an automobile in the event of a vehicle roll-over.
2. Description of the Related Art
It is known in the art to protect the occupants of a vehicle with an inflated restraint commonly referred to as an airbag. The airbag is in fluid communication with an inflator, which when activated, rapidly inflates the airbag with an inflation fluid. Airbags have been in use for a number of years to protect the front occupants of a vehicle from impacting the steering wheel, dash and/or the windshield during a front impact incident. And, airbags have recently been utilized to protect the occupants striking the side of the vehicle during side-impact and/or roll-over episodes. Those skilled in the art recognize that a major distinction between a roll-over air bag and a frontal or side impact air bag is that the frontal or side impact air bags are designed for extremely rapid deflation immediately following inflation. Contrariwise, a roll-over airbag, due to the nature of a roll-over incident, must maintain air pressure for a pre-determined amount of time in order to provide adequate protection to the vehicle occupant(s) during the roll-over episode. This sustained period of inflation under pressure requires a reinforced perimeter not found on typical frontal or side impact airbags. It will be appreciated that roll-over airbags, often referred to as xe2x80x9ccurtainsxe2x80x9d, and side-impact airbags are typically stored, either in the seat, in the side pillar, or proximate the conjunction of the headliner and the side panel of the vehicle in a deflated, and often folded, condition. For example, U.S. Pat. No. 5,529,332 issued to Wipasuramonton on Jun. 25, 1996, and U.S. Pat. No. 5,540,460 issued to Wipasuramonton on Jul. 30, 1996, each disclose a side-impact airbag which is inflatable into a position between a vehicle occupant and the side structure of a vehicle.
U.S. Pat. No. 5,909,895, issued to lino, et al. discloses a thermoplastic resin film bag. The background art section describes a conventional airbag having a reinforced joint face and teaches that the reinforcing cloth is a cylindrical body that is three-dimensionally arranged to a two dimensional join face in which production is troublesome and in which, if joined two-dimensionally, creates a problem with wrinkling the joint face.
What has heretofore been missing from the art is a roll-over self-inflating airbag that has a reinforced perimeter seal that is capable of sustaining the requisite pressure of the airbag for a predetermined period of time, and that is configured to limit the displacement of the sides from one another during expansion. What has also been missing from the art is a method of producing a reinforced joint, or seam, that can be sealed flat, without a problem of wrinkling the joint face, while still providing adequate reinforcement of the sealed edge.
Accordingly, it is an object of the present invention to provide a roll-over airbag that has perimetrically reinforced sealed edges.
Another object of the present invention is to provide a roll-over airbag that is configured so as to limit the displacement of the sides from one another during expansion of the airbag.
Still another object of the present invention is to provide a roll-over airbag that has a series of internal, reinforced tethers for limiting the displacement of the sides from one another during expansion of the airbag.
A further object is to provide a method for providing a sealed flat reinforcing lap joint along the sealed edges.
Other objects and advantages over the prior art will become apparent to those skilled in the art upon reading the detailed description together with the drawings as described as follows.
In accordance with the various features of this invention, a roll-over airbag is provided. The roll-over airbag of the present invention is defined by an inflatable air bag constructed of an upper fabric panel having a perimeter of a pre-selected length and a lower fabric panel perimetrically bonded to the upper fabric panel. In the preferred embodiment, this joint is reinforced with a lap joint so as to distribute the stress of rapid inflation over a larger surface area of the fabric and thereby transform an otherwise tear stress into a shear stress. In the preferred embodiment, the fabric material is a woven nylon, or other supported fabric, in which the interior has been treated with a urethane coating or other thermoplastic material that is reactive to high frequency energy, in order to be impermeable to the inflation fluid. During manufacturing, the lap joint and the perimetric edges are sealed flat by means of radio frequency (RF) bonding. At least one port opening is provided in the upper fabric panel for connecting the roll-over bag to an inflator to allow communication of the expansion fluid from the inflator to the roll-over airbag. Further, in accordance with the present invention, the process of bonding the lap joint prevents the lap joint from bonding to itself. In this regard, the lap joint is variously constructed of a material that prevents the bonding agent from bleeding through, constructed of a material having an impermeable agent adhered thereto, or has a template sandwiched between the upper and lower portions of the lap joint during the sealing process.
In addition to having perimeter reinforced inner seals, the roll-over airbag is constructed so as to limit the displacement of the upper and lower fabric panels from one another during inflation. In one embodiment, this is accomplished with at least one tether disposed within the airbag. Alternatively, the shape of the airbag and its perimetric contours can be selected for limiting displacement of the upper and lower fabric panels from one another. With the former, the tether has a first end bonded to the upper fabric panel and a second end bonded to the lower fabric panel. The length of the tether is preselected in order to determine the thickness and/or height of the expanded roll-over airbag. It will be appreciated by those skilled in the art that, in limited applications, it may be necessary to accommodate passage of a seat belt through the roll-over airbag, in such instances a passageway, having an expandable through opening, is disposed in the roll-over airbag.